Stringed loud speaker



NOV. 3, 1931. Q MlDHA-r STRINGED LOUD SPEAKER Filed Nov. 22. 1928 Patented Nov. 3, 1931 UNITED STATES CHAKIR MIDHAT, F BERLIN-EICHKAMP, GERMANY STRINGED LOUD SPEAKER Application filed November 22, 1928, Serial No. 321,256, and in Germany May 18, 1928.

The chief objections to the loudspeakers hitherto generally in use consist in that the harmonious upper oscillations are not well reproduced. The better loudspeakers reproduce the fundamental tones of the hearing range comparatively uniformly to the ear, but the harmonics, especially those of high frequencies, are very inadequately reproduced or not reproduced at all. The result of this imperfect reproduction of the harmonics is that all loudspeakers reproduce music peculiarly dull and lifeless, lacking the fineness and characteristic timbre of the original rendering.

All suggestions which have hitherto been made for improving the reproductions by altering the shape or the material of the diaphragm have not resulted in any satisfactory solution so that it appears that the problem of absolute uniform reproduction of the whole bearing range, including all harmonic higher oscillations, cannot be solved solely by the use of the diaphragm.

In the present construction of loudspeak- '25 ers a large-surface diaphragm is, therefore,

combined with a number of strings so that both diaphragms, as also the strings, are set in oscillation by the same driving unit. The

` harmonics produced by strings hereby merge with the fundamental tones, emanating chiefly from the diaphragm, and thus give the characteristic timbre of the instrument reproduced.

This solution appears particularly suitable owing to the fact that the main portion of musical renderings emanates from string vibrat-ions so that by using strings also in the reproducing instrument the greatest possible similarity between the music reproduced by the loudspeaker and the original rendering is ensured.

The invention is illustrated diagrammatically and by way of example on the accompanying drawings, on which Figure l is a front-view of a loudspeaker designed according to this invention; Figure 2 is a vertical cross-section through the same.

`As shown in Figs. l and 2, a plurality of strings 5 of different thickness is stretched so that they are fastened each at one end on the sounding boX`7 and at the other end to a centrally' situated, freely suspended disc 1. This disk is coupled with` the movable part of the driving unit 2 which may be either electromagnetic or electro-dynamic. If a modulated current flows through the loudspeaker, only those strings are set in resonance oscillation, of which the fundamental oscillation or one of the harmonics corresponds to the actual oscillating frequency of 1 the driving unit. If the frequency changes, the strings set in oscillation will thereby be immediately damped automatically. Therefore, no detrimental after-oscillation of the strings takes place. In order to prevent a 6* damping by mass inertia, it is necessary to make the disk l as small as possible, also as light as possible. For the sake of clearness it is illustrated in exaggerated size. This connecting member l need not absolutely be a circular disk as shown in the drawings, but may be of any suitable shape.

A loudspeaker made in this manner, having a suilicient number of strings, can also be used for reproducing music without anyy diaphragm whatever. As, however, this form of construction is naturally actually suitable merely for the reproduction of string instruments, it can only be used for special purposes. For general use it is necessary to combine the strings with a light large-surface diaphragm which may be of any suitable shape. In Fig. 2 a diaphragm 3 of conical shape is shown in dotted lines, which diaphragm, as also the central disk 1, is coupled with the driving unit. This form of construction is capable of reproducing all kinds of musical renderings in a very true manner.

Seeing the diaphragm and the system of strings can oscillate absolutely independently the one from the other, they do not distract each other but supplement each other, in a very eflicient manner. As in this arrangement the strings serve chiefly only to produce harmonics, their number need not be very large., because in the oscillation of each string, as is known, a very large number of harmonics occur. Therefore, a comparatively small number of strings (say from l() to 20) will suffice in order to give the necessarytimbre to the fundamental tones produced byy the diaphragm.

The strings only have a slightly distracting eiect with loud reproductions of speech. Therefore, it is advisable to provide some suitable device in order to damp or liberate the str-ings, as desired.

In Figure 2 is shown a damping member 4 which can be turned against, and away from, the string.

I claim:

1. A loudspeaker, comprising, in combination, a resonance body a plurality of strings stretched over a Wall of said body and being attached at one end to it; a freely suspended disk connected With the other ends of said strings, a driving unit coupled to said disk and being adapted to cause the strings to oscillate, substantially as set forth.

2. A loudspeaker, comprising, in combination, a resonance body provided with a wall,

a plurality of strings stretched over the Wall fill of said body; a large-sized diaphragm supported by said strings, and a drivingunit adapted to cause said strings, as Well as said diaphragm, to oscillate, substantially as set forth.r c

CHAKIR MIDHAT. 

